In a generator of a wind turbine, it is important to maintain an air gap between rotor and stator components as stable as possible to increase the efficiency of the wind turbine.
When a wind turbine has a direct drive generator, i.e. when it has no intermediate gear between the components directly driven by the wind and the generator, the circumference of the generator rotor is larger than that of a generator rotor in a wind turbine which has a gear. The purpose of the larger circumference is to have more active material to compensate for the rotor rotating less frequently. This enables such a “direct drive” wind turbine to generate as much electricity, or more electricity, as a wind turbine with a gear.
One of the challenges associated with direct drive wind turbines is maintaining an air gap between the rotor and stator of the generator. The air gap may be a radial or axial gap, depending on the design of the generator. Due to the magnetic force between the rotor and the stator, the rotor and stator are drawn to each other, thereby decreasing the air gap. In prior art solutions, bearings of different kinds have been mounted to the stator. The bearings rest against the rotor while it rotates to maintain the air gap.
Challenges still remain despite these attempts to address them. For example, the stator is a rigid and heavy component that resists being drawn toward the rotor. With some portions of the stator able to resist the forces and other portions deflecting slightly because they are not able to, the bearings may become somewhat tilted from their desired position. In this way, the optimal air gap between the stator and the rotor is not maintained and the bearings may be subjected to increase wear.